1. Field of the Invention
The invention is concerned with enhancing the cure of a dental restorative material, especially a photocurable material such as is used for making dental restorations. The invention also has nondental uses such as the restoration of art objects.
2. Description of the Related Art
Modern dental restorative materials typically are based on a plastic binder material and are cured by exposure to radiant energy, usually blue light within the range of 400 to 500 nm. Most such restorative materials contain an acrylate or methacrylate binder material, a filler such as quartz powder, and a photoinitiator. Representative dental restorative materials are described in U.S. Pat. No. 4,503,169 (Randklev), U.S. Pat. No. Re. 32,073 (Randklev), and U.K. Pat. Spec. No. 1,544,776.
Although such restorative mterials cure within a few seconds, air inhibits the cure so that a thin layer of soft, uncured or incompletely cured surface material must be removed by grinding or polishing. This has been avoided by covering the uncured restorative with a thin film that is transparent and impervious to air, e.g., a preformed film such as "Saran" wrap [poly(vinylidene chloride)] or a coating of glycerine. When using a preformed film, it can be difficult and tedious to assure complete coverage; and when using glycerine, some care is required to clean it away. Because of such difficulties, most dentists do not use any covering, but instead use an excess of the restorative material and grind away the excess, even though this takes time and the grinding involves a risk of damaging adjacent tooth surfaces. This also makes it difficult to attain accurate anatomical form, especially at mesio-distal or occlusal contact points.
A photocurable dental restorative material can be cured either in-the-mouth or out-of-the-mouth. For in-the-mouth curing, a hand-held visible light curing unit is used, typically consisting of a handpiece which contains a lamp and from which a fused glass fiber optic lightguide projects, or a desk-mounted light source from which a hand-held flexible fiber optic cable projects. Representative hand-held light curing units include the "Elipar" light from Espe, also shown in U.S. Pat. No. 4,298,806 (Herold); the "Visilux 2" light from 3M; and the light shown in U.S. Pat. No. 4,385,344 (Gonser).